Voltammetry of sparingly soluble metal complexes: a differential pulse polarographic study of the Zn(II)+oxalate system

An extension of a voltammetric model for the complexation between metal ions and mixtures of ligands (either simple or macromolecular, labile or inert) is proposed for the study of the Zn(II)+oxalate system. The model considers the presence of species of low solubility that can be assumed to behave as soluble inert complexes. As well as the solubility problem, a loss of reversibility in the zinc reduction process occurs. This problem is overcome by increasing the effective time scale of the measurements. The application of the model to experimental data has produced reliable results, which can be used to estimate complexation constants and solubility products, as long as the irreversible processes that influence the current and potential measurement are avoided.